The present invention relates to an improved method of suspension polymerising vinyl chloride or a mixture of a major proportion of vinyl chloride and remainder other monomers copolymerizable therewith, in an aqueous medium, in the presence of an oil soluble polymerization initiator and suspension stabilizer. More particularly, the invention relates to such a method which substantially reduces or eliminates the adhesion of polymeric dreg substance (hereinafter called sometimes scale) to the inner wall of a polymerization vessel used in the suspension polymerization.
In case of suspension polymerization of vinyl chloride or mixture of vinyl chloride and other monomers copolymerizable therewith, in an aqueous medium and in the presence of an oil soluble polymerization initiator, scales adhere to the inner wall of the reaction vessel, to the wings of the agitator, to the shaft of the agitator and to the interfering plates, etc. This decreases the yield of polymer and the cooling ability of the reaction vessel and decreases the property of the obtained product since the scale peeled off from the surfaces mentioned above may become mixed into the product. Moreover, such deficiency decreases the operation usage of the reaction vessel since substantial time and labor are required to remove the adhered scales. These disadvantages have always existed in conventional suspension polymerization methods of polymerizing vinyl chloride in an aqueous medium.